1. Field of the Invention
This invention pertains to graft copolymers made with 3-methacrylamidopropyldimethylammonium (MPDMA)/sulfonate ion pairs which are useful for absorbing aqueous electrolyte solutions. A further aspect of the invention relates to a method of using graft copolymers made with 3-methacrylamidopropyldimethylammonium/sulfonate ion pairs for absorbing aqueous electrolyte solutions.
2. Description of the Prior Art
Polymers for absorbing aqueous electrolyte solutions are used in numerous commercial and industrial applications. For example, polymers are used to improve the water absorbency of paper towels and disposable diapers.
Though known water absorbing polymers are highly absorbent to deionized water, they are dramatically less absorbent to aqueous electrolyte solutions such as salt water, brine, and urine. For example, hydrolyzed cross-linked polyacrylamide absorbs 1,024 grams of deionized water per gram of polymer, but only 25 grams of synthetic urine per gram of polymer. Cross-linked polyacrylate absorbs 423 grams of deionized water per gram of polymer, but only 10 grams of synthetic urine per gram of polymer. Hydrolyzed cross-linked polyacrylonitrile absorbs 352 grams of deionized water per gram of polymer, but only 25 grams of synthetic urine per gram of polymer. Analogous starch grafted copolymers generally have very poor absorbency to synthetic urine.
It would be a valuable contribution to the art to develop graft copolymers with high absorbency to aqueous electrolyte solutions. It also would be a valuable contribution to the art to develop inexpensive graft copolymers with high absorbency to aqueous electrolyte solutions. Furthermore, it would be a valuable contribution to the art to develop biodegradeable graft copolymers which were high absorbency to aqueous electrolyte solutions. The market for these types of copolymers is large and the uses are numerous. Therefore, seemingly small improvements in the absorbency translate into large savings in the quantity of copolymer required to absorb these liquids and large savings to the consumer.
Thus, it is a object of the present invention to provide graft MPDMA/sulfonate copolymers which are highly absorbent to aqueous electrolyte solutions.
Another object of the present invention is to provide highly biodegradeable graft copolymers which are highly absorbent to aqueous electrolyte solutions.
A further object of the present invention is to provide a method of using the graft copolymers of the present invention for absorbing an aqueous electrolyte solution comprising the step of contacting the graft copolymers of the present invention with the aqueous electrolyte solution.
Further objects, features, and advantages of the present invention will be readily apparent to those skilled in the art upon reading the description of the invention which follows.